AN EXPORTED INDUCER PEPTIDE REGULATES BACTERIOCIN PRODUCTION IN ENTEROCOCCUS-FAECIUM CTC492

Production of the bacteriocins enterocin A and enterocin B in Enteroco ccus faecium CTC492 was dependent on the presence of an extracellular peptide produced by the strain itself. This induction factor (EntF) wa s purified, and amino acid sequencing combined with DNA sequencing of the corresponding gene identified it as a peptide of 25 amino acids. T he gene encodes a prepeptide of 41 amino acids, including a 16-amino-a cid leader peptide of the double-glycine type. Environmental factors i nfluenced the level of bacteriocin production in E. faecium CTC492. Th e optimal pH for bacteriocin production was 6.2. At pH 5.5, growth was slow and very little bacteriocin was formed. The presence of NaCl or ethanol (EtOH) was also inhibitory to bacteriocin production, and at h igh concentrations of these solutes, no bacteriocin production was obs erved. The induction factor induced its own synthesis, and by dilution of the culture 10(6) times or more, nonproducing cultures were obtain ed. Bacteriocin production was induced in these cultures by addition o f EntF. The response was linear, and low bacteriocin production could be induced by about 10(-17) M EntF. This response was attenuated by lo w pH or the presence of high concentrations of NaCl or EtOH, and 300 t imes more EntF was needed to induce detectable bacteriocin production in the presence of 6.5% NaCl. High levels of bacteriocin production in cultures grown at low pH or in the presence of high concentrations of NaCl or EtOH were obtained by addition of sufficient amounts of EntF.